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2022 Vol. 47, No. 1

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2022, 47(1)

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2022, 47(1): 1-1.

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Acquisition technique for navigation signals based on pre-average process

ZHAO Bingfeng, ZHANG Linfeng, SUN Shouhao

2022, 47(1): 1-8. doi: 10.12265/j.gnss.2021061602

[Abstract](311) [FullText HTML] (150) [PDF 2723KB](58)

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To resolve large resource consumption and low Doppler resolution problem of traditional acquisition algorithm, a fast acquisition method based on pre-average and coefficient variable matched filter is proposed. The method stores the received intermediate-frequency signals and pseudo-code into corresponding dual-ports memory, completes correlation through coefficient variable matched filter, analyses the spectrum of correlation result by FFT. Finally, the maximum value of FFT output is verified to finish the Doppler estimation and acquisition process. The proposed method saves 50% hardware resources while reaching the same integration time, and can improve the Doppler resolution which can improve the probability of signal tracking. The experiment results show that this method can implement modern multi-frequency GNSS signals acquisition through the flexible configuration.

The design of BDS-3 B1 frequency point soft signal analog source

JIA Xiaohui, KE Jing, WANG Xue, ZHANG Zhimin

2022, 47(1): 9-17. doi: 10.12265/j.gnss.2021082001

[Abstract](407) [FullText HTML] (191) [PDF 8991KB](56)

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Through precise simulation of the complete signal process of the Global Navigation Satellite System (GNSS), a reasonable mathematical model of satellite signals is established to generate intermediate frequency signals in various environments, which can provide a good simulation and test platform for the evaluation of the service performance of the GNSS. Modularize and optimize the algorithm for each layer structure of the navigation signal. The navigation message module combined with track simulation software extrapolates the orbital parameters to ensure the authenticity of the message parameters. The data adopts the method of generating the signal in sections and then checking and superimposing. It ensures the alignment and superposition of the multi-layer structure of the signal, ensures the continuity of the signal code and the phase of the carrier, and ensures the stability of the analog source when generating a high sampling rate and long duration signal. The software receiver is used to analyze the signal to verify the effectiveness of the signal analog source.

Research on coordinate transformation model considering the spatial distribution of control points

HE Junkai, XU Dongsheng, WANG Mingyuan, LI Mingfeng

2022, 47(1): 18-22. doi: 10.12265/j.gnss.2021120204

[Abstract](283) [FullText HTML] (107) [PDF 2162KB](12)

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To guarantee the accuracy of coordinate transformation, a coordinate transformation model was studied through selecting the proper coincident points based on the spatial distribution of control points. With the models to describe the uniformity and density of control points set up, the influence of uniformity and density of coincident points on the accuracy of coordinate transformation model was discussed. A coordinate transformation model was constructed with the spatial distribution of control points taken into account, and the coordinate transformation process between the local coordinate system and CGCS2000 was discussed. At last, the effectiveness of the new model was verified with examples.

Decimeter-level positioning of intelligent terminal based on speed information constraint

KUANG Ye

2022, 47(1): 23-29. doi: 10.12265/j.gnss.2021102103

[Abstract](428) [FullText HTML] (154) [PDF 2840KB](47)

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With the development of location services, people’s demand for positioning accuracy continues to increase. At present, the positioning accuracy of smart phones is only at the meter level. In 2016, Google announced that it would allow developers to obtain mobile phone the Global Navigation Satellite System (GNSS) raw observation data, and it provided support for the research on mobile phone GNSS high-precision positioning algorithms. Since the pseudorange noise acquired by smart phones is relatively large, the accuracy of single-point positioning or pseudorange differential positioning using only pseudorange is limited, and it is difficult to achieve high accuracy. Therefore, on the basis of controlling the data quality, using the data output by the intelligent terminal, the speed is solved as the initial solution to constrain the coordinates. The accuracy of the speed measurement is analyzed, and the differential positioning is orgunized combing pseudorange and carrier. The experimental results show that the accuracy of velocity measurement is about 10 cm/s, which meets the positioning requirements of participating in the calculation as an initial solution. After the static simulation dynamic test results converge, the plane accuracy is 0.35 m, and the elevation accuracy is 0.59 m.The result of dynamic test is that the plane accuracy is 0.87 m, and the elevation accuracy is 1.09 m.The overall positioning result can reach the decimeter level.

Design of seismic ionospheric disturbance monitoring system based on ionospheric tomography receiver

ZHANG Yu, ZHU Fuying, YANG Jian, WANG Lanwei, ZHANG Xingguo

2022, 47(1): 30-35. doi: 10.12265/j.gnss.2021081002

[Abstract](239) [FullText HTML] (85) [PDF 5650KB](21)

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In order to better monitor the seismic ionospheric disturbance and extract the anomaly information, a seismic ionospheric disturbance monitoring system was developed based on the space ionospheric environment tomograph, which include a small area monitoring network and software system. It could output two-dimension total electron content (TEC), the maximum electron density (N_mF₂) and the corresponding peak height of the F2 layer (h_mF₂) distribution map with a spatial resolution of 1°×1°. When the ionospheric disturbance exceeds 10%, alarm will be presented. The seismic ionospheric disturbance monitoring system has realized the application demonstration of space ionospheric environment tomograph in the field of seismic ionospheric monitoring. It also provides the technical basis for its further promoted application.

Research on indoor fusion positioning algorithm based on SLAM/UWB

ZHOU Wei, SUN Xiankun, WU Fei

2022, 47(1): 36-42. doi: 10.12265/j.gnss.2021081802

[Abstract](568) [FullText HTML] (288) [PDF 2980KB](87)

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Accurate and stable autonomous positioning is the prerequisite for mobile robots to achieve autonomous navigation in indoor environment. Aiming at the cumulative error of visual simultaneous localization and mapping (SLAM) in indoor positioning and environmental factors that cause ultra wideband (UWB) positioning accuracy to decline, this paper proposes a SLAM/UWB-based indoor fusion positioning algorithm. First of all, the algorithm is based on the extended Kalman filter (EKF), fusing the UWB global positioning coordinates and the visual SLAM displacement increment. Then considering that the measurement noise is easily affected by the complex environment, threshold detection and adaptive measurement noise estimator are introduced to suppress the influence of abnormal values and time-varying measurement noise on the performance of the filter. Finally, an intelligent mobile car is used to conduct experiments in different indoor venues. Experiments show that the algorithm is better than a single UWB or visual SLAM positioning method, and has a more stable positioning effect than the traditional extended Kalman algorithm in a complex indoor environment.

Retrieving water surface height with high accuracy and reliability based on GNSS-R in reservoir area and its validation

SANG Wengang, LIU Yingchun, HE Xiufeng, WANG Zhaoran

2022, 47(1): 43-48. doi: 10.12265/j.gnss.2021062501

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The Global Navigation Satellite System Reflectometry (GNSS-R) providess a novel solution for water level monitoring with high temporal-spatial resolution. It has a great potentiality especially in our country, in large and medium-sized dams or high-steep slopes of reservoir banks, which GNSS deformation monitoring systems have been established. It can provide abundant data resources without extra hardware equipment. In this paper, the algorithm of satellite reflection signal inversion of water surface height is deduced based on GPS signal-to-noise (SNR) ratio data firstly. And then available satellites and section are determined and the trend term removal and Lomb-Scargle spectrum analysis is completed on this basis to provide a complete data processing process of inversion of water surface height. Through the actual measurement at the dam body and the flood gate of Wohushan reservoir in Jinan, the inverted water level is compared to the actual measured water level. The results demonstrate that the accuracy of the inversion height of the two separate stations reaches the centimetre level and meets the water level monitoring requirements. It also fully verified the feasibility and reliability of GNSS-R water level monitoring using the established GNSS deformation monitoring system in the dam and reservoir area.

Soil moisture model of Inner Mongolia based on GNSS ZTD and meteorological elements

LOU Zesheng, YANG Jing, WU Liang, SUN Yumei

2022, 47(1): 49-58. doi: 10.12265/j.gnss.2021090802

[Abstract](217) [FullText HTML] (101) [PDF 3248KB](15)

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Soil water content is an important indicator of drought in agriculture and animal husbandry, and has an important impact on climate and ecology. The change trend of soil water is of great significance for regional soil erosion and climate change research. But monitoring of soil water content in China is lagging. Thus, soil water content should be investigated using other existing data. In this study, the existing Global Navigation Satellite System (GNSS) zenith tropospheric delay (ZTD) and humidity, sunshine, and evaporation data in Inner Mongolia was used to investigate soil water content inversion. The correlation between each element and soil water content was analyzed. Noises was observed in the soil water content and GNSS ZTD data. Wavelet transform was used to eliminate the noises. After denoising, the correlation between soil water content data and each element was improved, and the correlation between soil water content and humidity is the best. The average correlation between the two experimental points is 0.645. Negative correlations are observed between soil water content and sunshine and evaporation, and their average correlations are −0.561 and −0.547, respectively. The correlation between soil water content and GNSS ZTD data is the smallest, with an average correlation of 0.271. Then, a soil water content model was constructed on the basis of the correlation between each element and soil water content, and its reliability was verified. The verified error statistics show that the NMWJ station model in the experimental area has the highest accuracy, with the accuracy of 90.1%, whereas the HLAR site model has the lowest accuracy, with 69.1%. The average accuracy of each station in the study area is 81.35%. The soil water content model based on multivariable elements can provide reference for the research on the change trend of soil water content. Reasonable distribution and utilization of water resources in the region can be conducted through the research on the change trend of soil water content to conserve water resources.

iGMAS multi-brand monitoring receiver data quality analysis

TENG Yuehao, JIA Xiaolin, LEI Panrong, ZHOU Ping, CAO Chuang

2022, 47(1): 59-67. doi: 10.12265/j.gnss.2021083104

[Abstract](329) [FullText HTML] (101) [PDF 3511KB](28)

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In order to verify the development status of GNSS receiver, fully confirm the receiver performance of the international GNSS monitoring and assessment system (iGMAS) monitoring station, and make contributions to the subsequent Global Navigation Satellite System (GNSS) receiver data quality assessment. Based on iGMAS multi-brand receiver comparative measurement experiment, the receiver performance and the quality of observation data were evaluated comprehensively by statistical analysis of the observation data quality (integrity rate, multipath, cycle jump ratio, observation noise) and the relative positioning accuracy of zero base line at different frequency points of multi-brand monitoring receivers. The results show that the data quality and performance of iGMAS monitoring station meet the corresponding standards. In terms of data integrity rate and multipath, the domestic brand receiver is basically equivalent to the foreign horizontal receiver. In terms of cycle jump ratio, pseudo-range, carrier phase noise and relative positioning accuracy of null base line, the domestic monitoring receiver is obviously better than the foreign monitoring receiver.

Comparison of three noise reduction methods for GNSS elevation time series

FAN Xiaomeng, HU Chuan, ZHANG Chongyang, LI Chenghong

2022, 47(1): 68-73. doi: 10.12265/j.gnss.2021090701

[Abstract](354) [FullText HTML] (161) [PDF 2509KB](28)

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In order to explore the noise reduction performance of the empirical mode decomposition (EMD), ensemble empirical mode decomposition (EEMD) and wavelet analysis, elevation time series data of different lengths from sin IGS stations are taken as examples. Firstly, the outliers and the trend items in the original data are removed to get the sample sequence meeting the experimental requirements. Then, the sample sequence is denoised by three methods and gets the real signal without noise. Finally, calculating the indexes of signal-noise ratio, correlation coefficient and root mean square error of data to compare the three noise reduction methods. The experimental results indicate that: 1) EEMD and wavelet analysis can well denoise when the quality of coordinate time series is poor. 2) Wavelet analysis has the best denoising performance on the Global Navigation Satellite System (GNSS) coordinate time series with time span of 5 a or 10 a; For 20 a time series samples, EEMD and wavelet analysis have similar denoising effects and are better than EMD. 3) The force of wavelet analysis to eliminate colored noise is better.

The influence of different calculation strategies on the establishment of GPS coordinate sequence noise model and speed

FU Jie, NIE Qixiang, HE Xiaoxing, CHEN Hongkang, XUN Changmin

2022, 47(1): 74-79. doi: 10.12265/j.gnss.2021091501

[Abstract](327) [FullText HTML] (119) [PDF 2392KB](17)

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The choice of solution strategy is closely related to GPS station speed and parameter model estimation. In this paper, 121 GPS reference stations under the land network are selected as the research object, and the akaike information criterion/Bayesian information criterion (AIC/BIC) optimal noise model evaluation criteria are used to discuss GAMIT, Bernese and their combined solution strategy (Comb) on the noise model and velocity estimation of the GPS coordinate sequence. The results show that different calculation strategies will have a certain impact on the GPS station parameter estimation results. In terms of the optimal noise model estimation, the GAMIT and Comb solution results mainly show the characteristics of the flicke noise+white noise (FN+WN) and power-law noise (PL)+WN models. The Bernese solution results show the characteristics of the FN+WN model in the east (E) and north (N) directions, and the characteristics of the PL+WN model in the up (U) direction; the influence of the solution strategy on the speed and speed uncertainty will be more significant in the U direction.

Research and application of renewal method of high speed railway horizontal control network

YUAN Da

2022, 47(1): 80-85. doi: 10.12265/j.gnss.2021080901

[Abstract](241) [FullText HTML] (130) [PDF 1931KB](16)

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According to the problem that the basic horizontal control network (CPI) of high-speed railway is updated continuously at multiple points during the operation period, resulting in a large number of updates of encrypted route horizontal control network (CPII) on high-speed railway line, a new method of updating CPI points based on stable CPI and encrypted CPII as constraint points is proposed. The engineering application shows that the proposed new method can better match the current situation of high-speed railway in the operation period, and reduce the renewal rate of encrypted CPII on the high-speed railway line; compared with the traditional methods, the results show that the update rate of the proposed new method is reduced by 7.3%, which verifies that the algorithm has great application value in the update calculation of encrypted CPII of high-speed railway.

Calibrate inter-channel bias in GLONASS/BDS combined pseudorange positioning

LUO Yuan, SU Benlei

2022, 47(1): 86-92. doi: 10.12265/j.gnss.2021101307

[Abstract](460) [FullText HTML] (232) [PDF 2706KB](38)

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Because of the frequency difference between GLONASS satellites, the hardware bias of the station cannot be absorbed by the receiver clock bias parameter. We presents a method to estimate a inter-channal bias for each satellites to improve the accuracy of combined GLONASS/BDS pseudorange standard point positioning. The solutions show that adding pseudorange ICB calibration can effectively reduce GLONASS positioning error, and the root mean square (RMS) value of east(E), north(N), and up (U) components error after calibration is reduced by 0.43 m, 0.69 m, 0.73 m, respectively, and the calibration effect is long-term effective. When the BeiDou Navigation Satellite System (BDS) observation conditions of the station is limited, the combined GLONASS/BDS pseudorange standard point positioning is effective in improve accuracy positioning. After calibrating inter-channal bias, dual-system positioning accuracy is further improved. And the RMS values of E, N, U components error are reduced by 0.37 m, 0.28 m, and 0.5 m, respectively.

CORS station application research in low-altitude UAV PPK technology processing

ZHOU Fengsong, CHU Bin, ZENG Xiangqiang

2022, 47(1): 93-97. doi: 10.12265/j.gnss.2021091701

[Abstract](448) [FullText HTML] (191) [PDF 2468KB](20)

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The application of postprocessed kinematic (PPK) technology in traditional unmanned aerial vehicle (UAV) requires temporary erection of ground base stations, which increases the workload of the field. The DJI Phantom 4 real time kinematic (RTK) UAV is used as the research object, the data of continuously operating reference stations (CORS) and ground base stations at different distances are used to participate in UAV PPK technology, and the processing results will be compared with UAV RTK. The results show that the relative results of CORS station are significantly affected by distance. When close to the experimental area, the accuracy of CORS base station is slightly lower than the results of base station and RTK erection in the experimental area, and can meet the requirements of 1∶1 000 scale mapping. This result is of certain significance to reduce the field work intensity and the field work flow.

A regional/single station ZTD combined forecasting model based on machine learning algorithm

YANG Xu, HE Xiangxiang, WANG Yuanyuan, TAN Fulin, CHEN Xiongchuan

2022, 47(1): 98-102. doi: 10.12265/j.gnss.2021072902

[Abstract](352) [FullText HTML] (146) [PDF 2167KB](34)

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Aiming at the temporal and spatial characteristics of zenith tropospheric total delay (ZTD), a combined regional/single station ZTD prediction model based on BP neural network and long-term memory network (LSTM) algorithm is proposed. Taking the observation data of 18 stations in Hong Kong continuously operating reference stations (CORS) network for 14 consecutive days as an example, the regional, single station and combined ZTD prediction models are studied by using BP neural network, LSTM and the algorithm proposed in this paper. The prediction results of HKWS station show that the root mean square error (RMSE) of regional, single station and combined ZTD prediction models are 10.2 mm, 10.4 mm and 8.5 mm respectively, and the prediction accuracy of the combined model is improved by 17.2% and 18.4% compared with the regional model and the single station model, respectively.

Extracting the temporal and spatial distribution characteristics of urban residents by using trajectory data

CHEN Weiliang, DU Jiusheng

2022, 47(1): 103-110. doi: 10.12265/j.gnss.2021081602

[Abstract](395) [FullText HTML] (218) [PDF 3261KB](50)

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A process of extracting the temporal and spatial distribution characteristics of urban residents by using taxi trajectory data is introduced, including: using the method of mathematical statistics to analyze the time-based characteristics of taxi boarding and alighting events; A density clustering algorithm integrating kernel density estimation (KDE) and point of interest (POI) classification is proposed, which realizes the mining of taxi loading and unloading hot spots and the discovery of the relationship between residents' travel activity law and urban functional areas. The research shows that the trajectory characteristics of residents show obvious differences between “work-rest” days and different periods, and this difference is closely related to the distribution of urban functional areas.

Research on antenna height correction for LGO to calculate the SOUTH static data

DAI Wei

2022, 47(1): 111-114. doi: 10.12265/j.gnss.2021072601

[Abstract](361) [FullText HTML] (217) [PDF 2140KB](27)

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The construction of smart cities requires accurate coordinates of the city's basic points, which are often statically solved by joint measurement with the local continuous operation reference station system (CORS). The LGO software of Leica is usually used for static calculation, and the LGO software cannot identify the antenna type of the the South Group’s GNSS receiver. When using LGO to calculate the southern static observation data, the antenna will be undefined, which will cause the antenna height error, affect the accuracy of baseline calculation and network adjustment, and result in elevation error. The reason for the antenna undefined problem is analyzed, and the influence of antenna height error on the GNSS static positioning accuracy is derived from the model. On this basis, suggestions and ideas for correctly obtaining the antenna height are put forward, which provides a reference for solving similar problems.

The current situation and development of the commonly-used geocentric coordinate system in China

LIU Guangming, HU Yu, SHA Feng, XIE Guojun, CHENG Wei

2022, 47(1): 115-120. doi: 10.12265/j.gnss.2021082701

[Abstract](433) [FullText HTML] (471) [PDF 1943KB](97)

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In this paper, the current status of CGCS2000, BeiDou coordinate system (BDCS) and WGS-84 coordinate system in common use in China is introduced, the connection and difference between them are analyzed, the existing problems and limitations are pointed out, and some suggestions for the further development of CGCS2000 and BDCS in China are put forward by referring to foreign experience. CGCS2000 reference frame has been established for more than 20 years. It is not current and is more suitable for 2D coordinate application scenarios requiring unity and stability. Therefore, it should be maintained continuously and updated regularly. There are tens of thousands of continuously operating refererce station (CORS) in China, and it is necessary and conditional to establish a real-time reference frame in China for higher precision 3D coordinate application scenarios. For a long time, people used to refer to the Global Navigation Satelite system (GNSS) coordinates as WGS-84, which became synonymous with the geocentric coordinate system. In production practice, it is not important which coordinate system a geocentric coordinate belongs to, but the three elements of a geocentric coordinate must be focused on, such as precision, calendar element and frame. There is no essential difference between BDCS and WGS-84. Based on the practice of NGA, the concept of BDCS ground-based and space-based reference frame is expanded to make BDCS global, current and accurate at the same time. The role of the BDCS reference framework after concept extension is equivalent to “WGS84+IGS”. In digital Earth, 3S integration, smart city and other applications, CGCS2000 and BDCS dual benchmark services can be adopted. Based on THE CGCS2000 base map, the expanded BDCS benchmark can be used in high-precision applications, which can take into account the standards and the current situation, and meet the needs of globalization and precision.

Development status and trend of United States of America military satellite navigation user equipment

LIU Dongliang, LU Jing, ZHENG Zixia, ZHANG Song

2022, 47(1): 121-126. doi: 10.12265/j.gnss.2021071401

[Abstract](227) [FullText HTML] (202) [PDF 2234KB](61)

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United States of America satellite navigation user equipment has been applied in many fields and has played a key role in recent wars. Focusing the United States of America military satellite navigation user equipment, this paper analyzes the current situation of the first, second and third generation of GPS user equipment, summarizes the development characteristics of GPS user equipment, and puts forward the development trend of GPS user equipment, which can be valuable reference value for the development of China’s satellite navigation terminal equipment.